Dielectrics, resistors, capacitors, inductors, electrical and thermal conductors, and similar-type electronic components or devices can be made from thick film compositions, referred to as “pastes”, that are used to form thick film elements often by means of screen-printing techniques.
Generally, a thick film composition comprises a functional phase that imparts appropriate electrically functional properties to the composition. The functional phase comprises electrically functional powders dispersed in an organic solvent containing a polymer. These compositions will typically contain a binder, e.g., a glass frit. Such a composition is fired to burn out the polymer and solvent and to impart the electrically functional properties. However, in the case of a polymer thick film (PTF) composition, the polymer remains as an integral part of the composition after drying and only the solvent is removed. A processing requirement may include an heat treatment such as curing as known to those skilled in the art of polymer thick film technology.
Increasingly, such PTF compositions are required to consist of a polymer highly soluble in useful solvents with relatively low (unwanted) water sorption. As used herein, “sorption” is intended to mean adsorption and/or absorption. The compositions are desirably processed, i.e., cured at relatively low temperatures, such as, 150 to 200° C.
There is a need for polyimide-based thick film composition to satisfy these needs and particularly for such compositions containing non-fluorinated polyimides.